I f\ "n 1^ 



VI 



\y 



DEPARTMENT OF COMMERCE 



Technologic Papers 



OF THE 



Bureau of Standards 

S. W. STRATTON DIRECTOR 



No. 188 

SOME properties OF WHITE METAL BEARING 
ALLOYS AT ELEVATED TEMPERATURES 



BY 

JOHN R. FREEMAN, Jr., Associate Physicist 
R. W. WOODWARD, Physicist 

Bureau of Standards 



APRIL 5 , 1921 



2/-^t.4 0^ 




PRICE. 5 CENTS 

Sold only by the Superintendent of Documents, Government Printing Office 
"Washington, D. C. 

WASHINGTON 
GOVERNMENT PRINTING OFFICE 

1921 



Cf-) 



t^ 



jjjlvHiugrapIv 



-^BRARY OF CONGRESS 






SOME PROPERTIES OF WHITE METAL BEARING 
ALLOYS AT ELEVATED TEMPERATURES 

By John R. Freeman, Jr., and R. W. Woodward 



ABSTRACT 

An apparatus is described for determining the yield point and ultimate strength 
of white metal bearing alloys at temperatures up to ioo° C. A new design of heating 
apparatus is described for determining the Brinell hardness of metals at temperatures 
up to ioo° C. 

The results of compression tests and Brinell hardness tests at temperatures up to 
100° C are given for five typical white metal bearing alloys, including three tin-base 
alloys, one lead-base alloy, and one intermediate alloy, which show that the tin-base 
alloys maintain their properties better at elevated temperatures than the lead- 
containing alloys. 

Results of tests are given which indicate that up to 5 per cent of lead in a high-grade 
babbitt does not affect the yield point or ultimate strength at 25 or 75° -C. 

The yield point of tin-base alloys is not affected by heating for six weeks at about 
100° C, but the yield point is lowered in the lead-base alloy by heating for two weeks 
at about 100° C. 



CONTENTS 

Page 

I. Introduction 4 

II . Preparation of alloys 5 

1 . Metals used 5 

2 . Alloying procedtire 5 

III. Preparation of test specimens 6 

IV. Apparatus used for testing 6 

1 . Compression tests 6 

2 . Brinell hardness tests 8 

V. Preliminary tests 9 

VI. Elevated-temperature compression tests 10 

VII. Elevated-temperature Brinell tests 12 

VIII. Discussion of results 13 

1 . Compression tests 13 

2 . Brinell hardness tests _. 14 

IX. Effect of prolonged heating at 100° C 15 

X. Effect of small percentages of lead 15 

XI. Summary and conclusions 16 

33333°— 21 - 



4 Technologic Papers of the Bureau of Standards 

I. INTRODUCTION 

The mechanical properties of white metal bearing alloys have 
been the subject of several investigations with the particular 
object of establishing the relations between the properties obtained 
in laboratory tests and the ultimate test of service. Practically 
all of these tests reported in the literature on white metal bearing 
alloys were conducted at room temperature, the Brinell hardness 
alone ' having been determined for a few alloys under other con- 
ditions of temperature. While we therefore have considerable 
knowledge of the mechanical properties of these alloys at ordinary 
temperatures, our knowledge of their properties at elevated 
temperatures is very limited. 

The importance of knowing the properties of bearing alloys at 
elevated temperatures is readily appreciated when one considers 
that the oil temperature in the crank case of an automobile engine 
may often reach 60° C, and that bearing temperatures of 100° C 
and higher have been measured in similar engines. 

It is the purpose of this paper to present the design of new 
apparatus and the results of tests to determine the mechanical 
properties in compression and the Brinell hardness of some 
representative white metal bearing alloys at elevated tempera- 
tures. 

The nonferrous metals division of the Society of Automotive 
Engineers is proposing as standard white metal bearing alloys 
the four compositions given in Table i . 

TABLE 1. — Specifications for White Metal Bearing Alloys Proposed by the Society 

of Automotive Engineers 



Components 



S.A.E. 
No. 10 


S. A. E. 
No. 11 


S. A. E. 
No. 12 


Per cent 


Per cent 


Per cent 


90-92 


86-89 


Remainder 


4-5 


5-6.50 


2. 25- 3. 75 


4-5 


6-7. 50 


9.50-11.50 


<0.35 


<0.35 


24-26 



S. A. E. 

No. 13 



Tin 

Copper... 
Antimony 
Lead 



Per cent 

4.50-5.50 

<0.50 
9. 25-10 75 
84-86 



These four alloys and A. S. T. M. alloy No. 2^ were selected as of 
representative composition suitable for this investigation. It will 
be noticed that A. S. T. M. alloy No. 2 (Table 2) is very similar 



• Jesse L. Jones, Babbitt and babbitted bearings, A. I. M. M. E. Trans., 60, p. 458; 1919. 

2 "Tentative specifications for white metal bearing alloys," Proc. A. S. T. M., 19, pt. i, p. 469. 



Bearing Alloys at Elevated Temperatures 5 

to the S. A. B. alloy No. 1 1 . The properties of these two alloys are 
compared here, as the A. S. T. M. alloy was considered by the 
S. A. E. committee as a little hard. 

The results of chemical analyses ^ of the five alloys studied are 
given in Table 2 . 

TABLE 2. — Percentage Composition of Alloys Studied 



Components 


Bearing 
metal No. 1 : 

S. A. E. 

No. 10; 

A.S.T.M. 

No. 1 


Bearing 

metal No. 2: 

A. S.T.M. 

No. 2 


Bearing 

metal No. 3: 

S. A. E. 

No. 11 


Bearing 

metal No. 4: 

S. A. E. 

No. 12 


Bearing 
metal No. 5; 

S. A. E. 

No. 13; 

A. S. T. M. 

No. 9 


Copper 


Per cent 

4.56 

4.52 

Remainder 

None 

<0.05 


Per cent 

3.51 

7.57 

Remainder 

None 

<0.05 


Per cent 

5.65 

6.90 

Remainder 

0.09 

< .05 


Per cent 
2.90 
10.50 
Remainder 

25.05 
< .05 


Per cent 


AtiHmnny 


10.03 


Tin.. 


Remainder 


Lead 


84.95 


Iron , . . 


< .05 







II. PREPARATION OF ALLOYS 

1. METALS USED 

Pure Banka tin and the best grade of "Star" antimony were 
used. Neither these metals nor the copper were analyzed, as 
the freedom of the alloys from impurities is proof of the purity of 
the metals used. 

Analysis of the commercially pure lead used showed the fol- 
lowing: Lead, 99.94 per cent; copper, 0.03 per cent; antimony, 

< 0.03 per cent. 

2. ALLOYING PROCEDURE 

Alloys Nos. 1 , 2 , 3 , and 4 were prepared by first melting the 
tin in a plumbago crucible in a gas furnace and then adding the 
requisite amounts of a 50 per cent Sn.-5o per cent Cu hardener 
and metallic antimony. After addition of the alloying elements 
the temperature of the bath was carried up to the melting point 
of antimony and stirred to instire a homogeneous alloy. The 
temperature of the melt was then allowed to drop to about 500° C 
with continual stirring of the metal, which was then poured into 
a cast-iron mold. The surface of the bath was always kept covered 
with charcoal to prevent excessive oxidation. The temperature 
was measured by means of a specially calibrated chromel-alumel 
thermocouple connected to a portable potentiometer. 

2 J. A. Scherrer, of the Bureau of Standards, made all chemical analyses reported in this paper. 



6 Technologic Papers of the Bureau of Slanidards 

The lead-base alloy No. 5 was similarly prepared, but in this 
case the lead was first melted and then the metallic tin and 
antimony were added. 

The alloys were made up to meet the mean composition of the 
specifications, and the resultant compositions given indicate how 
close a desired composition may be obtained with the careful 
laboratory methods used. 

III. PREPARATION OF TEST SPECIMENS 

The compression test specimens used were small cylinders 1% 
inches long by about >2 inch diameter (1.5 by 0.514 inch), this 
ratio of length to diameter being within the limits recommended 
by the A. S. T. M., and the cross section for these experiments 
being easily tested in a 10 coo-pound testing machine. These 
specimens were tinned in a lathe, with a hollow mill, from cast- 
ings 2 inches long by ^ inch diameter which were made by 
pouring the metal from the desired temperature into a split 
steel mold of the above dimensions. 

The samples for Brinell testing were similar to those used by 
Lynch," the metal being poured into an open steel mold 2 inches 
in diameter by ^ inch deep, but in this case the mold was not 
previously heated before poiuring, always being at room tempera- 
ture when the metal was first poured. Before making the impres- 
sions, the faces of the casting were turned off and the test then 
made on the bottom face. Three impressions were made on each 
casting at equidistant points on a circle one-half the radial distance 
from the center. The average of these three readings was taken 
as the Brinell hardness under the given conditions. 

IV. APPARATUS USED FOR TESTING 

1. COMPRESSION TESTS 

The cylinders were compressed in a standard Reihle 10 000- 
pound testing machine. 

The deformation per imit load was measured by a specially 
designed compressometer. A copy of a photograph of this 
instrument moimted on a specimen is shown in Fig. i. The 
frame and uprights are made of alumintun. They are held to 
the specimen by three small steel screws, having conical points, 
set radially in the same plane, and spaced equidistantly around 

* t. D. Lynch, "Study of bearing metals and methods of testing," A. S. T. M., 13, p. 699; 1913. 



Bureau of Standards Technologic Paper No. IE 




Fig. I. — Compressometer mounted on specimen 



Bearing Alloys at Elevated Temperatures 



Mead of Testing Machine 




Fig. 2. — Assembly drawing of a section of heating bath, showing original dimensions 



8 



Technologic Papers of the Bureau of Standards 



the specimen, as may be seen in the photograph. The small 
U-shaped block is a gage used for spacing the frames at the proper 
distance on the specimen. The gage length or the distance be- 
tween the planes of the screws is i inch. 

The " Last Word " dials used read to approximately thousandths 
of an inch (one division on dial = 0.00087 in.) , and ten thousandths 
are readily estimated. 

The assembly and important dimensions of the bath used for 
heating the specimen during tests are shown in Fig. 2, which is 

a section through the center. 
The specimen A is compressed 
between the steel posts B B. 
Dtiring test the specimen with 
compressometer attached is 
immersed in a heated liquid 
(glycerin was found very satis- 
factory) held in the container 
C. £> is a Silphon diaphragm. 
This collapses like an accordion, 
permitting the top of the con- 
tainer C to drop below the 
level of the base of the speci- 
men. This is a particularly 
convenient method for lower- 
ing the bath to place a spec- 
imen in position for testing, 
especially as it eliminates the need for any packed joints. A pho- 
tograph of the entire apparatus with a specimen in position for 
testing is shown in Fig. 4. 

The bath is heated with a small size Hot-Point electric heater 
immersed in the glycerin. The glycerin was forced in a continuous 
stream over the heater by a small electric motor-driven propeller. 
This continuous stirring of the glycerin and the ready control of 
the heating current with a variable resistance provided excellent 
control of the temperatm'e of the specimen during the test. In 
all cases the temperature of the bath and consequently the speci- 
men did not vary by more than 2° C during a test. 

2. BRINELL HARDNESS TESTS 

The Brinell hardness tests were made with a standard Brinell 
machine using a 500 kg load on a 10 mm ball applied for 30 sec- 
onds. For the elevated temperattire tests the apparatus shown 
in Fig. 3 was used. It is simply a suitable container for the heat- 




Brinell 
Test I ng 



Fig. 3. — Apparatus for Brinell hard- 
ness testing at elevated temperatures 



Bureau of Standards Technologic Paper No. 188 




Fig. 4. — Specimen with compressometer and heating bath assembled in testing inachine 



Bearing Alloys at Elevated Temperatures 9 

ing liquid (glycerin was used) with a base made to fit on the 
spherical seat of the Brinell machine and a post on the inside to 
support the specimen away from the bottom and permit good 
circulation of the liquid around it. The bath was stirred with a 
small motor-driven propeller and was heated by a small resistor 
placed on the bottom of the container. During test the entire 
specimen was submerged, the Brinell ball also being completely 
immersed. Sufficient time was always allowed for the specimen 
to reach the temperature of the bath, this having been previously 
determined by inserting a thermocouple in a specimen and noting 
the time elapsed between the placing of the specimen in the bath 
and when the center reached the temperature of the bath. 



V. PRELIMINARY TESTS 

It is well known that the pouring temperature of a bearing metal, 
all other conditions being constant, has a marked influence on the 
mechanical properties. In view of this fact, preliminary to any 
test at elevated temperatures, the effect of pom-ing temper attue 
on the compressive strength at room temperature was determined 
for alloys Nos. i, 3, 4, and 5. The results obtained from com- 
pression tests are given in Table 3. 

TABLE 3. — Effect of Pouring Temperatures on Yield Point and Ultimate Strength in 

Compression of Various Alloys 



Alloy No. 


Pouring 
temperature 


Yield point 


Ultimate 
strength 


1 


°C 

400 
446 
495 
390 
44S 
500 
300 
350 
400 
300 
356 
404 


Lbs./in.2 
3750 
4000 
3500 
3500 
4250 
4000 
5000 
4250 
4750 
3250 
3750 
3250 


Lbs./in.2 
12 940 


3 


12 855 

13 500 
15 830 


• 
4 


16 435 
15 830 
14 015 


5 


13 685 
13 635 
13 840 




15 020 
15 245 



In results reported in this paper the yield point was adopted 
arbitrarily as at >^ of i per cent reduction of the gage length. 
The ultimate strength was arbitrarily chosen as the unit load 
necessary to produce a deformation of 25 per cent of the original 



lo Technologic Papers of the Bureau of Standards 

length of the test specimen. The reasons for selecting these 
values will be discussed later. 

From a comparison of the results of Table 3 and the pouring 
temperatures suggested in the tentative specifications of the 
A. S. T. M.^ the following temperatures were used in casting test 
specimens for all further tests. 

Pouring 
temperature, 
°C 
No. I 440 

No. 2 440 

No. 3 440 

No. 4 345 

No. 5 325 

VI. ELEVATED-TEMPERATURE COMPRESSION TESTS 

Stress deformation curves were taken on all five alloys at room 
temperature (20-30° C), 50, 75, and 100° C. At least two speci- 
mens were tested under each condition to provide a check. 

Representative stress-strain curves at the four temperatures of 
each alloy except No. 2 are given in Fig. 5. These show the type 
of stress- deformation curve obtained with the apparatus described 
in this paper and also show -very clearly the marked change in the 
compressive strength of the alloys with increasing temperatures. 

On the plot a "dial unit" is equivalent to 0.00087 inch and is 
the algebraic mean of the total deformation shown by the indi- 
vidual dials for any given load. 

A study of the curves shows that it is practically impossible 
to pick out a limit of proportionality as ordinarily determined by 
noting the departure of the stress-deformation curve from a 
straight line, and, further, we know that the finer the measure- 
ment the lower will be this point. An arbitrary yield point was 
therefore determined upon. After comparing the yield points 
indicated by several values of percentage reduction of gage length 
the value of yioi 1 per cent of the gage length (0.00125 inch) was 
adopted for purposes of compaiison, as it generally seems to 
coincide with the first marked yielding of the specimens tested. 
This value 0.00125 inch) is practically equivalent to 1.5 division on 
the dial or "dial units" used on plot (Fig. 5). 

When soft metals of this type and size of test specimens are 
compressed they do not eventually shear but continue to flatten 

^ See footnote 2. 



Bearing Alloys at Elevated Temperatures 



II 



>0 









o 



Oo 



o°. 



oo 



1°' 
'ooo. 



0,0 



°Oo„ ' 

1 °00o, 



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0,0 



xSo 
I 



0. i°°°r<'°°o<,_ 



O o 



>oJ '"po-oooio 



o o 



° o ' 



o o o ( 



i 



o 

■oO 



' On ' I 

"° OO OO o oo 



I 



I 



I 



T 



1 

o o 



T 



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o 




o 




s 




■y 




s 




a 




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■S 


'o 


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fn 


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u/ hg J3c/ q-j ui 3399aj:f_Q ^^iss9jdiUo^ 



12 



Technologic Papers of the Bureau of Standards 



out with increasing loads, so it is necessary to adopt some arbi- 
trary values for ultimate strength which will at least be comparable 
among themselves. A reduction of 25 per cent of length was 
chosen in this investigation as at this value in all cases the load 
had become nearly constant for increasing deformation. In the 
case of high lead alloys the load generally reached a maximimi 
value and then fell off before the 25 per cent reduction was reached. 
In these cases the maximum load was recorded. The values of 
yield point and ultimate strength thus obtained are given in 
Table 4. 

TABLE 4. — ^Yield Point and Ultimate Strength in Compression at Elevated Tem- 

perattires 



Alloy 
No. 



Property 



Values in pounds per square inch at- 



25° C 



50° C 



75° C 



100° C 



Yield point 

Ultimate strength 

Yield point 

Ultimate strength 

Yield point 

Ultimate strength 

Yield point 

Ultimate strength 

Yield point 

Ultimate strength 



4 400 
12 850 

6 250 

15 175 

5 750 

16 425 
4 700 

13^85 

3 750 

15 020 



3 800 
10 400 

4 850 
11850 

5 000 
12175 

3 650 
10 035 

2 650 
11275 



3 150 

8 450 

4 000 

9 400 
4 250 

10 100 
2 900 
7 845 
2 250 
7 920 



2650 
6950 
2850 
6825 
3350 
7725 
2150 
6045 
1550 
4770 



VII. ELEVATED TEMPERATURE BRINELL TESTS 



The Brinell hardness of alloys Nos. i, 3, 4, and 5 was deter- 
mined at room temperature, 50, 75, and 100° C. The values 
obtained are given in Table 5. 

TABLE 5. — Brinell Hardness at Elevated Temperatures 



Alloy No. 


Brinell hardness numeral at— 


25° C 


50° C 


75° C 


100° C 


1 


a 17. 2 (28. 6) 
22.3 
22.4 

19.7(19.5) 
22.3(28.3) 


13.8 
18.2 
15.8 
16.8 


11.1 
14.8 
11.3 

11.4 


8.2(12.8) 
11.3 


3 


4 


7.5 


5 


8.2 (8.6) 


2. . . . . 













o A. S. T. M. specifications (see footnote 2) give the values shown in parentheses. 



Bearing Alloys at Elevated Temperatures 
VIII. DISCUSSION OF RESULTS 



13 



1. COMPRESSION TESTS 

For greater convenience of comparison the yield points of the 
four alloys are plotted against temperature in Fig. 66. 

As one would expect from the composition, the yield point of 
alloy No. 3 is considerably higher at all tempera tm-es than the 
other alloys. The yield point of No. 3, however, falls off more 









1^ 



I6000 

I4000 

/zooo 
/oooo 

6000 
6000 


"■Alloy hlo.1 
\ *'AlloyNo.3 


\ +'AlloyNo.4- 
A \ 1'= Alloy Mo. 5 


i^5\ 


^N^^;\^ 


"^^C\ 


"^^ 





ZS' 



SO' 



75° 



lOO' 'C 



a 






«5 



sooo 



o = Alloy No.l 
« = Alloy M>.3 
+ • Alloy KoA 
<» " Alloy Afo.5 



^ 40O0 



3000 



ZOOO 




Fig. 6 a and 6. — Curves showing effect of temperature on yield points and ultimate strength 

of alloys Nos. I, J, 4, and 5 

rapidly than No. i with increasing temperatures. The points in 
both these cases appear to lie on a straight line. This is not the 
case with alloys Nos. 4 and 5, which contain lead. For both of 
these alloys the yield point seems to drop off more rapidly at first, 
between 25 and 50° C. It is significant to note that while the 
yield point of alloy No. 4 is higher than No. i at room temperature, 
it is lower at 50° C and decreases at a more rapid rate between 
25 and 100° C than does No. i , and that the yield point of tin-base 
alloys is higher at all temperatures above 50° C. 



14 



Technologic Papers of the Bureau of Standards 



The yield point of alloy No. 2, curves of which are not given, 
is slightly higher at room temperature than that of No. 3, but at 
50° C its yield point is slightly less than No. 3, and so, if the bearing 
heats to 50° C or over, any advantage gained by using No. 2 alloy 
in a bearing is lost in so far as the yield point is concerned. 

There are given in Fig. 6a curves showing the variation of 
the ultimate strength with the temperature. Here, as with the 

yield point, alloy No. 3 



oAlhyNo.1 
X Alloy No. 3 
■•t-AlloyNo.4 
H-AlhyNo. S 




has the maximum value 
throughout the tempera- 
ture range, and alloys 
Nos. I and 3 maintain 
their strength better, hav- 
ing a higher ultimate 
strength at temperatures 
above 60° C than either 
alloys Nos. 4 or 5, which 
contain lead, even though 
the ultimate strength of 
No. I at room tempera- 
ture is less than that of 
^s' SO' 75' too- c Nos. 4 or 5. The ulti- 

FiG. 7. — Curves showing relation of Brinell hardness mate Strengths of the 
to temperature for alloys Nos. i, 3, 4, and 5 |^^^ allovS at IOO° C 

stand in the same relation to each other as their respective 
yield points. 

2. BRINELL HARDNESS TESTS 

It is noted that the Brinell hardness values obtained for the 
tin-base alloys are considerably lower than those usually given. 
This difference may be due to the small percentage of impurities 
in the alloys used in this investigation as compared with similar 
alloys as ordinarily prepared. 

Ciurves showing the variation of the Brinell hardness with tem- 
perature are given in Fig. 7. Here, again, alloy No. 3 has a maxi- 
mum value throughout the temperature range. There is no 
evident relation between the relative magnitude of either the 
ultimate strength or yield point and the Brinell hardness. 

The hardness of alloys Nos. 4 and 5, however, drops off very 
rapidly with increasing temperature, while Nos. i and 3 maintain 
their hardness, both having a greater hardness at 100° C than 
No. 4, and No. i having the same value as No. 5 at this temperature. 



Bearing Alloys at Elevated Temperatures 
IX. EFFECT OF PROLONGED HEATING AT 100° C 



15 



Oftentimes a babbitted bearing which has given good service 
will foi no apparent reason gradually become soft and " wipe out." 
As a working hypothesis it was thought that this failure with age 
might be due to softening from prolonged heating causing an 
annealing action. In order to determine the validity of this 
tentative hypothesis, compression specimens of alloys Nos. 1,3, 
4, and 5 were heated in an oil bath for from one to six weeks at 
temperatures between 90 and 100° C. They were then tested at 
room temperature with the results given in the following table: 

TABLE 6. — Effect of Prolonged Heating on the Yield Point in Compression 





Yield points of the various alloys 


Days heating at 100° C 


Alloy 
No. 1 


Alloy 
No. 3 


Alloy 
No. 4 


Alloy 
No. 5 





Lbs./in.2 
4550 
4500 
4600 
5025 
4900 


Lbs./in.2 
5750 
5500 
5800 
5650 
5950 


Lbs./in.2 
4650 


Lbs./in.2 
3750 


7 


3450 


14 


4250 
4750 
4850 


3200 


28 


O2800 


42 


3150 







"2 One specimen only. All other values are the average of two specimens. 

A study of the above table indicates that for alloys Nos. 1,3, 
and 4, heating at 100° C for 42 days has no appreciable effect on 
the value of the yield point when the specimens are cast in the 
manner indicated. For alloy No. 5, however, there is a very 
evident decrease in the value of its yield point with the prolonged 
heating which, however, evidently takes place in the first two 
weeks of the heating. 

X. EFFECT OF SMALL PERCENTAGES OF LEAD 

The specifications for high-grade, tin-base alloys such as Nos. 
1,2, and 3 call for a low lead content generally not to exceed 0.35 
per cent. 

Many believe, and one investigator ® has presented experimental 
evidence, that percentages of lead even up to 5 per cent are not 
harmful but possibly beneficial. The authors have therefore 
investigated the effect of small percentages of lead on the yield 
point and ultimate strength of No. 2 alloy at room temperature 
and at 75° C. 

' Jesse L. Jones; see footnote i. 



019 971 507 



i6 



Technologic Papers of the Bureau of Standards 



The alloys were prepared by adding metallic lead to the No. 2 
babbitt in amounts shown by the chemical analysis given, together 
with the yield points, in Table 7. 

TABLE 7. — Effect of Lead on Compressive Strength 




Percentage of lead 


Yield point at— 


Ultimate strength 
at— 




25° C 


75° C 


25° C 


75° C 


0.00 


Lbs./in.2 
6150 
5850 
5750 
6300 
6000 
5850 


Lbs./in.2 
4000 
3700 
3300 


Lbs./in.2 

15 175 
15 640 
14 025 


Lbs./in.2 
9 395 
10 010 
9 765 


0.26 


0.51 


1.01 


1.25 


4100 
3850 


16 380 
15 330 


10 600 
9 725 


5.04 







The addition of amounts up to 5 per cent of lead to this babbitt 
seems to have no very appreciable effect on its mechanical proper- 
ties in compression at room temperature or at 75° C tmder the 
conditions of test used. The authors think, however, that these 
tests should not lead to an increase in the lead content tolerance 
in tin-base bearing metal specifications until much more work is 
done along this line and particularly to determine the possible 
effect of small percentages of lead on the resistance to repeated 
impact. 

XI. SUMMARY AND CONCLUSIONS 

An apparatus is described for determining the yield point and 
ultimate strength of white metal bearing alloys at temperatures 
up to 100° C. A new design of heating apparatus is described for 
determining the Brinell hardness of metals at temperatures up to 
100° C. 

The results of compression tests and Brinell hardness tests at 
temperatures up to 100° C are given for five typical white metal 
bearing alloys, including three tin-base alloys, one lead-base 
alloy, and one intermediate alloy, which show that the tin-base 
alloys maintain their properties better at elevated temperatures 
than the lead-containing alloys. 

Results of tests are given which indicate that the addition of 
amounts up to 5 per cent of lead in a high-grade babbitt does not 
affect the yield point or ultimate strength at 25 or 75° C. 

The yield point of tin-base alloys is not affected by heating for 
six weeks at about 100° C, but the yield point is lowered in the 
lead-base alloy by heating for two weeks at about 100° C. 

Washington, November 6, 1920. 



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